JP2888171B2 - Electronic balance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic balance, and more particularly, to an electronic balance having a roberval mechanism.

[0002]

2. Description of the Related Art Generally, in an electronic balance, a sample dish 20 is connected to a sample tray 20 through a roberval mechanism (also referred to as a parallel guide) 10 as shown in FIG. 3 as a side view (A) and a plan view (B). By supporting, the sample tray 20 is regulated so as to be displaced up and down while maintaining the horizontal position, so that an error due to the uneven displacement of the sample with respect to the sample dish 20, that is, an so-called eccentric error (four corner error) does not occur. Is considered.

The roberval mechanism 10 has a structure in which a movable portion 13 is connected to a fixed portion 14 via upper and lower beams 11 and 12 having flexible portions E serving as hinge portions at both ends. 20 is supported by the movable part 13. The load acting on the sample dish 20 is applied to a load sensitive unit 40 such as a balanced electromagnetic force generator via a lever 30 connected to the movable unit 13.
Is transmitted to For small weighing electronic balances,
The movable part 13 may be directly connected to the load sensitive part 40 without using a lever.

[0004] By the way, such a roberval mechanism 10
In general, the parallelism between the upper and lower beams 11 and 12 is important. Under the condition that the upper and lower beams 11 and 12 are exactly parallel, the eccentricity error of the load on the sample Is eliminated. That is, an eccentricity error occurs unless the dimensions H and H 'in FIG. 3A are strictly adjusted so as to match. This adjustment is not of the degree that can be performed by measuring the dimensions of H and H 'and making them equal to each other, for example, in the case of a precision electronic balance, which requires accuracy of the order of μm or less. At work, sample plate 2
While moving the load placed on the zero, fine adjustment of the parallelism is performed so that the weighing value does not change at each position.

As a mechanism for adjusting the parallelism of the Roberval mechanism as described above, conventionally, as shown in FIG. 4, a flexible portion e whose one end is more likely to bend in the vertical direction than the other portion.
The adjusting arm 71 is fixed to the fixing portion 14 through the other end, and the other end is a free end. An adjusting screw 72 screwed into the fixing portion 14 is penetrated near the free end of the adjusting arm 71. with, one of the upper or lower beam the fixed end near the adjusting arm 71, for example, fixed above the beam 11, the displacement L of the vertical direction caused by the rotation of the adjusting screw 72 to the L ₂ / L ₁ In general, the mounting portion F of the beam 11 is finely moved by being reduced. Such an adjustment mechanism is provided at each of two mounting portions F of the one beam 11 to the fixing portion 14.

[0006]

Incidentally, in actually adjusting the eccentric error by the conventional adjusting mechanism of the Roberval mechanism as described above, particularly in the direction indicated by the arrow P in FIG. It is difficult to adjust to an eccentric load in a direction orthogonal to the direction in which the beam 12 extends (hereinafter, referred to as the left-right direction), and the vertical movement of the beam mounting portion F by the adjustment screw 72 can be considerably finely adjusted. Even with the use of one, it often happens that the adjustment limit is reached.
That is, an error of the same polarity occurs regardless of whether the load is moved in the left or right direction, or if the load is once applied and returned to the center,
The limit at the center cannot be adjusted, for example, the value at the center cannot be restored.

The present invention has been made in view of such circumstances, and has as its object to provide an electronic balance that can easily and precisely adjust an error with respect to an eccentric load in an arbitrary direction.

[0008]

A configuration for achieving the above object will be described with reference to FIGS. 1 and 2 which are drawings of an embodiment. An electronic balance according to the present invention comprises a roberval mechanism 1.
An adjusting mechanism 50 for adjusting the parallelism of the upper and lower beams 11 and 12 is fixed to the fixed portion 14 via flexible portions e1 and e2 whose both ends are more easily bent in the vertical direction than the other portions. An adjusting arm 51 having one end of one of the upper and lower beams (11) fixed near one end thereof;
The arm 5 is disposed near the other end of the arm 51.
1 is characterized by being constituted by an interval adjusting mechanism 52 for adjusting the interval in the vertical direction between the other end of the first unit 1 and the fixing unit 14.

[0009]

The reason that it is difficult to adjust the eccentric load in the left-right direction of the roberval mechanism in the conventional structure is that the two right and left adjustment mechanisms interposed between the beam mounting portion F and the fixing portion 14 are used. The adjusting arm 71 is cantilevered by the fixed portion 14 via the flexible portion e. That is, due to the eccentric load in the left-right direction, a force for rotating or twisting acts on the flexible portions e of the left and right adjustment arms 71, whereby each adjustment arm 71 bends and the two mounting portions F It is because each height changes mutually.

The present invention has been made by paying attention to this point. The adjusting arm 51 is attached to the fixed portion 14 via the flexible portions e1 and e2 at both ends which are more easily bent in the vertical direction than the other portions. By supporting and holding, the rigidity of the adjusting arm 51 against rotation or twisting is improved, the rigidity of the adjusting arm 51 against bending load or twisting against an eccentric load in the left-right direction is improved, and the adjusting arm 51 is rigidly supported. Deflection is greatly reduced.

Here, since the adjusting arm 51 is provided with flexible portions e1 and e2 which are easily bent in the vertical direction at both ends thereof, the movement is particularly affected when the distance adjusting mechanism 52 moves the fixing portion 14 in the vertical direction. There is no.

[0012]

1A and 1B are explanatory views of the overall structure of an embodiment of the present invention. FIG. 1A is a side view, and FIG. 1B is a plan view. FIG. 2 is an enlarged perspective view of the adjusting mechanism 50.

The roberval mechanism 10 has the same structure as the conventional structure shown in FIG. 3, and is fixed to the movable portion 13 by upper and lower beams 11 and 12 each having a flexible portion E at each end. The sample tray 20 is supported on the movable part 13. Further, similarly to the conventional case, the load acting on the movable portion 13 is transmitted to the electromagnetic force generating device 40 which is a load responsive portion via the lever 30, and
The displacement of the lever 30 is detected by a displacement sensor (not shown), and the current flowing through the electromagnetic force generator 40 is controlled such that the displacement detection result is always zero. Then, the load on the sample dish 20 is obtained from the magnitude of the current.

An adjusting mechanism 50 for adjusting the parallelism of the Roberval mechanism 10 is provided at each of two mounting portions F to the fixing portion 14 of the upper beam 11 of the Roberval mechanism 10.

The adjusting mechanism 50 includes an adjusting arm 51 having one end fixed to one end of the upper beam 11 of the roberval mechanism 10, and the other end of the adjusting arm 51 and a fixing portion 14.
Adjustment mechanism 5 for adjusting the vertical distance between the camera and the camera
2.

The adjusting arm 51 is fixed to the fixed portion 14 via flexible portions e1 and e2 whose both ends are more likely to bend in the vertical direction than the other portions. The upper beam 1 is placed on the upper surface close to the other flexible portion e2.
One end is fixed. Further, an interval adjusting mechanism 52 is provided at a position slightly closer to the flexible portion e1 side from the flexible portion e2.

The interval adjusting mechanism 52 is composed of an adjusting screw 52a and a compression coil spring 52b.
2a is screwed into a female screw formed in the fixing portion 14 through a through hole formed in the adjusting arm 51. Also, coaxially with the adjusting screw 52a, a compression coil spring 52 is provided between the upper surface of the fixing portion 14 and the lower surface of the adjusting arm 51.
b is inserted.

In the above arrangement, when the adjusting screw 52a is rotated in either direction, a force acts on the adjusting arm 52 in either upward or downward direction at the position where the adjusting screw 52a is disposed. Since the screw 52a is close to the flexible part e2, the adjusting arm 51 is substantially rotated and displaced along the vertical plane about the flexible part e1, and the vertical direction at the position where the adjusting screw 52a is disposed. To the distance between the flexible part e1 and the adjusting screw 52a, and
The size is reduced at a rate corresponding to the ratio of the distance between the flexible portion e1 and the mounting portion F of the beam 11, and the height of the mounting portion F of the beam 11 changes by a small amount.

In the embodiment of the present invention, the eccentric load on the sample dish 20 in the left-right direction, for example, as shown in FIG.
When a load is applied to the position indicated by the point Q in (B), the upper beam 11 exerts a force to twist the point Q side downward and the other side upward with the center line C interposed therebetween. The right and left adjustment arms 51 act to twist in the same direction via the left and right attachment portions F, but each adjustment arm 51 can be used not only at the attachment portion F side of the beam 11 but also at the opposite end. Since the adjustment arm is fixed to the fixing portion 14 via the flexible portion e2, the adjustment arm is fixed to the fixing portion 14 via the flexible portion only on the attachment portion F side of the beam 11, as shown in FIG. The amount of twist of the adjusting arm 51 is greatly reduced as compared with the case of FIG. As a result, the height of the left and right mounting portions F with respect to the fixing portion 14 of the beam 11 hardly changes even by the eccentric load in the left and right direction, such as the application of a load to the point Q, and the adjustment screw 52a Adjustment arm 51 even in position
Is hardly displaced in the up-down direction, so that the conventional problem does not occur when adjusting the deviation error in the left-right direction.

Here, in the embodiment of the present invention, both ends of the adjusting arm 51 are fixed to the fixing portion 14, but both end portions are fixed via flexible portions e1 and e2 which are easily bent in the vertical direction. Therefore, when the arm 51 is displaced in the vertical direction due to the rotation of the adjustment screw 52a, the adjustment can be performed with a relatively light force without obstructing the displacement.

In the above embodiment, the interval adjusting mechanism 5
2, a compression coil spring 52 that elastically presses one end of the adjustment arm 51 upward in addition to the adjustment screw 52a.
However, the present invention is not limited to this, and the height of the adjusting arm 51 and the height of the attachment portion F of the beam 11 to the fixing portion 14 (the lower side The distance between the beam 12 and the mounting portion to the fixed portion 14) is determined by the height of the mounting portion of the beam 11 on the movable portion 13 side (the distance from the mounting portion of the lower beam 12 to the movable portion 13). If the height is set to be slightly higher (larger), the height adjustment is always performed by displacing the adjustment arm 51 downward by the adjustment screw 52a, so that the elasticity of the adjustment arm 51 is used. In this case, the compression coil spring 52b can be dispensed with.

In the above embodiment, the adjusting mechanism 50 is provided on the upper beam 11 side. However, the adjusting mechanism 50 may be provided on the lower beam 12 side. Furthermore, the shapes of the upper and lower beams 11 and 12 of the roberval mechanism 10 are substantially Y-shaped as in the above-described embodiment.
For example, the upper and lower beams 1 are not limited to
1 and 12 may be a pair of left and right sides, and both ends may be attached to the movable part 13 and the fixed part 14, respectively. An adjustment mechanism 50 exactly the same as that described above may be provided for each.

[0023]

As described above, according to the present invention,
One of the beams of the Roverbal mechanism is fixed, and both ends of the adjusting arm, the distance of which is adjusted to the fixed part by the distance adjustment mechanism, are fixed to the fixed part via flexible parts which are easily bent in the vertical direction. Even if an eccentric load is applied in the direction (left-right direction) perpendicular to the direction in which the beam of the mechanism extends, a force that twists the adjustment arm works,
The actual amount of twist is significantly reduced as compared with the adjusting arm of the conventional cantilever support structure. As a result, the height of the mounting portion of the beam to the fixed portion is less likely to change due to such an eccentric load, and the work of adjusting the eccentric error is significantly simplified, and, as a result, the high accuracy with a small eccentric error Electronic balance can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the overall structure of an embodiment of the present invention, wherein (A) is a side view and (B) is a plan view thereof.

FIG. 2 is an enlarged perspective view of the adjustment mechanism 50;

FIG. 3 is a side view (A) and a plan view (B) showing the configuration of a general mechanism of an electronic balance having a roberval mechanism.

FIG. 4 is an explanatory view of a parallelism adjusting mechanism of a conventional Roberval mechanism using an adjusting arm.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Roberval mechanism 11, 12 Beam 13 Movable part 14 Fixed part E Flexible part 20 Sample dish 30 Lever 40 Electromagnetic force generator (load sensitive part) 50 Parallelism adjusting mechanism 51 Adjustment arm e1, e2 Flexible part 52 Interval adjustment Mechanism 52a Adjustment screw 52b Compression coil spring

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01G 21/24 G01G 23/01

Claims (1)

(57) [Claims] A rotatable mechanism having a movable portion connected to a fixed portion via upper and lower beams parallel to each other and having flexible portions at both ends, wherein a sample plate is supported by the movable portion; In the electronic balance in which the movable portion is connected directly to the load sensitive portion via the lever, the electronic balance has an adjustment mechanism for adjusting the parallelism between the upper and lower beams of the roberval mechanism, and the adjustment mechanism includes both ends. An adjustment arm in which each of the beams is fixed to the fixing portion via a flexible portion that is more likely to bend in the vertical direction than the other portion, and one end of the beam is fixed near one end thereof. An electronic balance, which is arranged near the other end of the arm and configured by an interval adjusting mechanism that adjusts a vertical interval between the other end of the arm and the fixed portion.